The present invention relates to the artificial illumination arts. It finds particular application in providing high ignition voltages for portable lamp ballasts and will be described with particular reference thereto. It is to be appreciated, however, that the present invention is also applicable to boosting voltages in fixed ballasts and other circuits, and is not limited to the aforementioned application.
Typical portable lamp ballasts utilize relatively low-cost, low-voltage sources to operate the lamp. For instance, certain types of popular fluorescent camping lanterns utilize four xe2x80x9cDxe2x80x9d cells. In other words, the lantern has a six volt source. Typically, much larger voltages are needed to ignite and sustain a lighted fluorescent lamp. Inexpensive fluorescent lamps, as are commonly found in such lanterns, require on the order of about 200 Volts to ignite. Consequently, when these systems initiate start-up, extremely high circulating currents are present in resonant tanks of the ballast, and relatively high-valued circuit components are required to meet the voltage demands for lamp ignition.
In addition to having high startup currents, typical portable ballasts are inefficient. As a result of limited voltage available from direct current sources, typical portable lamps utilize light sources that require less voltage to ignite, but are more inefficient, lessening light output and battery life.
In accordance with one aspect of the present invention, a lighting ballast is provided. A voltage source provides current that is converted by a switching portion, the switching portion including first and second transistors. A drive portion is included. A resonant load portion receives a lamp, and a transformer boosts the voltage from the switching portion to the resonant load portion.
In accordance with another aspect of the present invention, a method of igniting a lamp is included. A threshold voltage is supplied by boosting a signal significantly higher than its direct current source. The direct current is converted into alternating current by a switching portion, the switching portion including first and second transistors.
In accordance with another aspect of the present invention, a portable lamp ballast is provided. A direct current battery provides power to the ballast. A complementary pair of MOSFETs convert the direct current signal from the battery into an alternating current signal. A drive inductor taps power from a resonant inductor. A transformer including primary and secondary windings boosts the alternating current signal to the lamp.